NS On-Site Sewage Disposal Systems Technical Guidelines

Finalized Changes On-site Sewage Disposal Systems Technical GuidelinesSummary Document April 2013

NS On-site Sewage Disposal Systems Technical Guidelines:

Finalized Summary of Changes April2013

PRIMARY CONTACT:

Leah Boutilier, P. Eng, PhD

Acting On-site Services Program Coordinator

(902)722-5185

5151 Terminal Road

P.O. Box 442

Halifax, NS

B3J 2P8

Targeted consultations were performed in January and February 2013with EMC Staff and the On-site Sewage Industry on proposed changes to the Nova Scotia On-site Sewage Disposal Systems Technical Guidelines. Please refer to the Summary of Changes documentthat outlines the proposed changes. This document summarizes the finalized changes including justification based on the comments that were raised during the consultation period. Once approved by NSE, an updated version of the Technical Guidelines will be posted to the Nova Scotia Environment website and available for purchase through your local NSE Office.

A number of comments and recommendations outside of the proposed changes were received during the consultation period. This document focuses on finalizing the proposed changes only as changes cannot be made without consultation. Although these comments may not be addressed in this revision of the Guideline, they will be considered for future analysis and improvement.

1. Subject: Replacement of a malfunctioning system with a sloping sand filter, irrelevant bullet points removed or modified

During the last revision of the guidelines in 2009, the sloping sand filter was permitted for use on any lot, not just for a malfunction replacement. Bullet points discussing sand filter application as a replacement for a malfunction were removed from section 2.9 based on a recommendation from EMC staff as these points were missed during the last revision of the guidelines.

This change was overall supported during the consultation period with minor wording revisions recommended.

2.9REPLACING A MALFUNCTIONING SYSTEM

First bullet removed. Second bullet was edited to remove the specific reference to a sloping sand filter design.

Bullet 2 (previously) now bullet 1 reads:

If a Qualified Person level II cannot select a system to fit on the lot, then a Qualified Person Level I may be able to design a system for the lot.

Bullet 4 (previously) was edited, now bullet 3 reads:

When a sloping sand filter or innovative system is utilized as the replacement system and results in a point surface discharge, the replacement system can only be designed or selectedfor the existing sewage loading from the structure. Point Surface surface discharge will only be permitted where subsurface distribution of effluent is not possible and risk to public health is minimal.

Last bullet removed:

If the replacement system being proposed is to include an increase in sewage loading than a sloping sand filter or innovative system cannot be utilized. In these cases an on-site system as described elsewhere in these guidelines, excluding a holding tank or privy, must be employed and will be considered providing the system is designed or selected for the proposed loading and the meets the requirements of the Regulations Respecting On-site Sewage Disposal Systems. REMOVED

1. Subject: Septic tank size requirements increased to accommodate peak flows (tank to be sized based on 4 day retention time at average flows) based on a recommendation from a consultant report.

In general EMC Staff and Industry supported the proposed increase in minimum tank size; 3 out of 17 respondents were opposed to the proposed change. Those in support of the increase in minimum tank size raised concerns surrounding additional costs, ability to install larger tank sizes due to confining geological conditions and/or machinery capability.Questions were also raised as to whether there is a problem with our current tank sizing guideline?Additional research suggests the current 2 day retention time calculation is standard in residential septic tank design. Considering research findings and the septic tank effluent filter addition, the proposed increase in minimum septic tank capacity has been excluded. Larger tank sizes are still recommended in the guideline.

Other recommendations include the ability to use multiple tanks in series or parallel to achieve the required capacity in limiting conditions. This should be allowed regardless of the increase in tank size, wording has been revised to accommodate the option of utilizing multiple tanks to achieve the desired capacity.

3.1.1Septic Tanks

Any septic tank is required to meet the following specifications: (Figure 3A)

1.All tanks must conform to the latest edition of Standard CAN/CSA-B66-00 or the latest revision, published by the Canadian Standards Association.

2.It must include a watertight access for purposes of maintenance, inspection, and pump-out.

3.Septic tanks for dwellings must have a total capacity not less than that stated in Table 3.1. For larger systems the minimum capacity should be:

●For average daily flows up to 9000 l/day: Vtank(1) = 4Q2Q

Where: Q - average daily flow in litres

Vtank - total tank volume in litres*

●For average daily flows 9000 l/day or more: Vtank(2) = 9000 + Q

Where: Q - average daily flow in litres

Vtank - total tank volume in litres*

*Vtank may be achieved by one or multiple tanks in series or parallel; design volume represents total minimum capacity.

The minimum required septic tank size capacity is 4000 2800 L. Septic tank sizes capacities larger than the required minimum may reduce problems and extend the life of an on-site system.

TABLE 3.1

MINIMUM CAPACITY OF SEPTIC TANKS FOR DWELLINGS

Number of Bedrooms / Minimum
Liquid Capacity (litres)
Up to3
4
5 / 40002800
54003300
68004500

1. Subject: Required septic tank effluent filter based on recommendation from a consultant report.

All respondents were in favor of the change torequire a septic tank effluent filter but it was recommended to be accompanied by an extensive homeowner education campaign as filters require on-going maintenance. Lack of maintenance could potentially result in sewer back-ups;therefore it is crucial that homeowners understand their responsibility with respect to filter maintenance. It was recommended that documentation be required stating that the homeowneracknowledges their septic tank has an effluent filter and requires maintenance. Most QPs who specify an effluent filter as part of their system already include this type of documentation as part of their homeowner package; an example letter should be developed to assist industry in this transition.

Other recommendations include easy at grade access to pump and siphon chambers as well.

Bullets 5 through 7 in section 3.1.1 were edited to address clarity with respect to easy access to the septic tank including the effluent filter. Text was also added to section 3.1.3 to encourage bringing the pump or siphon chamber riser to grade; see change #5 (dosing and pump chamber capacity).

3.1.1Septic Tanks

5.Access to a tank may must be provided by a single opening at the center outlet of the tank to provide effluent filter access, but two openings—over the inlet and outlet—are recommended for easier service. The dimension of any opening shall meet CSA requirements.

6.If the top of the tank is more than 150 mm below finished grade, a riser must be provided to extend to within 150 mm of finished grade. TheA riser may shall be extended to the ground surface provided and the cover fitted with a suitable locking mechanism.and tThe area around the riser is should be graded to divert surface water away from the riser.

7.The top of a septic tank must be at least 150 mm and not more than 1500 mm below finished grade or as specified by the manufacturer’s instructions.

12.All residential septic tanks are required to have a septic tank effluent filter that meets NSF Standard 46 (components of wastewater treatment systems) and has easy accessat finished grade at over the outlet of the septic tank for filter maintenance. A properly fitted effluent filter will decrease the risk of solids entering the disposal field and prolong life of the system.

1. Subject: Use of recycled crushed glass as a replacement for imported or filter sand

All respondents supported the proposed change with questions surrounding the need for the unused crushed glass to be removed from the site. A review of local recycled crushed glass product safety information suggests that crushed glass manufactured to meet sand permeability specifications does not presentmoreof a safety hazardthan sand. Additional minor wording changes were needed to repair a previous error in the guideline (particle size corrected, previously read 25mm, should be 2.5mm).

Questions were also raised with respect to future considerations for failed septic systems containing crushed glass and whether the product would be considered acceptable for burial on residential properties. Discussions with NSE’s Solid Waste branch confirmed that the use of recycled crushed glass in on-site system construction would not be considered a means of disposal and therefore acceptable. In the event of a malfunctioning on-site system containing crushed glass, materials should be handled in a similar way if the field were constructed with sand.

3.3.2Imported Sand Fill

The following requirements apply to:

●the buffer in a distribution system, i.e., C2 and raised C2

●the construction of all above ground systems, i.e., a C3 and a mound

This material shall:

●if it is a naturally occurring or manufactured sand or sandy gravel or a washed sand or recycled crushed glass, have a permeability, as placed on site, between 0.00003 and 0.0005 m/sec, as determined by the falling head permeability test (Appendix B) and have a maximum particle size of 2.5 mm.

●when designing or selecting a system with a specified fill permeability within the above acceptable range of 0.00003 and 0.0005 m/sec; the Qualified Person 1 shall ensure that fill with the specified permeability range required by the selection or design is availableused in system construction.

3.3.3Filter Sand and Sloping Sand Filter Material

The following requirements apply to:

●The layer of sand (filter sand) installed under the crushed rock in all systems

●The sand used to construct a sloping sand filter

This material shall:

●be a washed concretemanufactured sand that meets the current ASTM-33 or CSA A23.1 specifications or

●be a naturally occurring or washed manufactured sand or recycled crushed glass having a permeability, as placed on site, between 0.0001 and 0.0005 m/second as determined by the falling head permeability test (Appendix B) and have a maximum particle size of 2.5 mm.

3.3.4Safety Considerations for use of Recycled Crushed Glass

When using recycled crushed glass as a replacement for imported or filter sand in an on-site sewage disposal system, the QP must ensure its permeability meets the requirements outlined in Sections 3.3.2 & 3.3.3 for its intended purposeuse.Please note the following safety considerations:

●Unused crushed glass shall be removed from the site when the installation has been completed.

●Qualified persons and installers intending on using the crushed glass in on-site sewage disposal systems in Nova Scotia shall be knowledgeable of the material safety information provided by the manufacturer.

1. Subject: Clarification Table 3.32: Siphons and Maximum Dosing Volumes and Pumps–Dosing and Chamber Capacity

Only 5 comments were received on this minor change; 4 were from EMC Staff, and one from Industry. Comments from EMC Staff included questions around the need for the “below any horizontal seam” note and suggestions that the “Dosing Amount per Discharge Event” column should be considered the maximum dose volume and more frequent dosing at lower volumes should be encouraged. The Industry representative’s comments recommend micro dosing (at least 20 times per day), highlighted potential problems caused by dosing infrequently at large volumes and questioned the need to specify siphon/dosing chamber capacity.Additional analysis would be required to specify dosing volumes for selected systems but slight wording changes have been made to encourage more frequent dosing at lower volumes.

3.1.3Pump and Siphon Chambers

The pump or siphon chamber discharge capacity must be sized to distribute effluent over the entire disposal field during each dose. This allows utilization of the entire field and minimizes the possibility of breakout of effluent in a localized area. Periodic dosing also allows the infiltrative surface to drain between doses. These cycles of alterative dosing and resting may maintain higher infiltration rates in the clogging mat and thus extend the life of the system.

The normal dosing frequency should be a minimum of two times per day for a system that is selected. More frequent lower volume doses are recommended.When a large system is designed, other dosing frequencies may be necessary. The discharge volume must be large enough to flood the entire distribution pipe. Unless the level 1 or 2 qualified person specifically selects the pump to be used, it is the installers responsibility to ensure that the pump has the proper capacity of achieving equal distribution throughout the field.

A typical pump chamber is shown in Figure 3.C and shall conform to Canadian Standards Association specification CAN/CSA-B66-00 or the latest revision.

Requirements for a pump chamber include:

1.The liquid capacity of the chamber shall provide a liquid volume below any horizontal seam,storageequal to one days flow.

2.The chamber shall be equipped with an audible and visible high level alarm, level controls, and other accessories required to assure its effective and reliable operation.

3.If the top of the tank is more than 150 mm below finished grade, a riser must be provided to extend to within 150 mm of finished grade. Extending the riser to ground surface is recommended and must include a cover and locking mechanism.

…..

Requirements for a siphon chamber include:

1.If the top of the tank is more than 150 mm below finished grade, a riser must be provided to extend to within 150 mm of finished grade.Extending the riser to ground surface is recommended and must include a cover and locking mechanism.

3.5PUMPS AND SIPHONS

3.5.1General

When a pressure distribution system is required, the siphon or pump should be designed to flood the disposal field a minimum of twice per day— . make sure the entire pipe is completely filled and under pressure.More frequent lower volume doses are recommended - ensure the entire pipe is completely filled and under pressure.

TABLE 3.2

SIPHONS AND MAXIMUM DOSING VOLUMES AND PUMPS - DOSING AND CHAMBER CAPACITY

Flow / MAX Dosing Amount per
Discharge Event in Litres / Minimum Pump
Chamber Capacity*
1000 L / 500 L / 1000 L
1350 L / 675 L / 1350 L
1500 L / 750 L / 1500 L

*below any horizontal seamMore frequent lower volume doses are recommended

1. Subject: Alternative/Innovative On-site Wastewater Treatment Technologies

The majority of respondents supported the proposed requirements for alternative technologies but a number of questions were raised surrounding clarity of the requirements. Wording changes were made throughout this section to clarify questions raised during the consultations. Industry representatives recommended a mechanism be established to ensure continuity of the operation and maintenance contract for subsequent homeowners. This will require discussions with municipalities and should be explored further.

3.9APPROVED PRODUCTS

Products for use in on-site sewage disposal must be approved by Nova Scotia Environment, unless theandproduct system installations shall meets the requirements outlined in Section 3.10. Manufacturers or suppliers who wish to market their product in NS that meets the criteria outlined in Section 3.10 are asked to submit a product summary and manual to the On-site Services Program Coordinator. The On-site Coordinator will confirm the product meets requirements and classify the productbeforeaddingitto the Province’s list of approved products.

Keep second paragraph in this section as is.

3.10ALTERNATIVE/INNOVATIVE ON-SITE SEWAGE TREATMENT TECHNOLOGIES

On-site sewage system installations including Alternative an alternative wastewater treatment technologies technology must satisfy all of the following requirements to be marketed in Nova Scotia for the purpose of on-site sewage treatmentand disposal:

• A proven on-site wastewater treatment technology that has undergone third party testing and is recognized by at least one of the following certifications:
• BNQ Standard NQ 3680-910 Stand-alone Wastewater Treatment Systems CLASS II Secondary treatment minimum requirement.
• NSF 40 Residential Wastewater Treatment System Class I
• Alternatively, third party testing may be completed (e.g. NS On-site Wastewater Research Centre, Truro, NS) for a minimum of 12 consecutive months. The manufacturer or supplier is responsible for the cost of testing and shall submit a report to Nova Scotia Environment summarizing treatment performance. Treated effluent must meet or exceed the BNQ and NSF effluent quality requirements.
• Flow equalization is provided either as part of the treatment unit or incorporated into the system design to ensure peak and intermittent flows do not disrupt treatment performance.
• Application for on-site approval must be submitted by a Professional Engineer licensed to practice in Nova Scotia.
• System must be installed by an installer certified by the Province of Nova Scotia.
• Complies with the Nova Scotia On-site Sewage Disposal System Regulations.
• Meets Nova Scotia Environment’s On-Site Sewage Disposal Systems: Technical Guidelines.
• Manufacturer or supplier Provides provides the department and on-site industry with an a design and installation manual that includes operation and maintenance instructions. Manual must contain sufficient information for the installer to construct the system properly and according to the manufacturer’s specifications.
• Active systems (systems treatment units including any mechanical/moving components: e.g. pumps, aeration) must include an Operation and Maintenance (O&M) contract between the homeowner and a qualified persondesignated professional to ensure proper function of the proposed system for the life of the system. The designated professional must be trained and deemed qualified by the product manufacturer or supplier and have an understanding of on-site sewage treatment. The requirement of an O&M contract must be outlined under the terms and conditions of all On-site Sewage Approvals for Alternative/Innovative technologies including active components.It is the responsibility of the homeowner and the manufacturer/supplier to maintain the O&M contract after the system has been constructed.
• No point surface discharge of treated effluent will be permitted; treated effluent must be discharged subsurface and the dispersal bed area (infiltration area) designfollowing based on the requirements outlined in the manufacturer’s engineering/design manual or as described in Table 3.3. Surface discharge may be considered when replacing a malfunction only if the proposed lot cannot accommodate subsurface disposal and only upon approval by NSE.
• NOTE Table 3.3 Max Vertical Hydraulic Loading of Treated Sewage Effluent is for dispersal bed area design of vertical flow systems only. :
• Dispersal bed area design shall be based on the lowest permeable soil and have a minimum of 600 mm of permeable soil. Imported sand fill may be used to achieve 600 mm of permeable soil and/or improve infiltration in low permeable soils.

Lateral flow contour systems system area must be designed based on soil permeability and Darcy’s law, as described in Chapter 5 of this Guideline.